Basophilic leucocytes: structure, function and role in disease.

We have attempted to review the current state of our knowledge concerning the human basophilic leucocyte, drawing on experimental data derived from animals when necessary. Long neglected, a great deal has been learned about these cells in recent years, about their morphology, their biochemical constitutents and their ability to synthesize certain of these constitutents, their interactions with homocytotropic antibodies, their release of mediators in anaphylaxis, their response to chemotatic stimuli, their participation and progressive degranulation in cell-mediated hypersensitivity reactions, and their capacity for ingesting and releasing certain exogenous tracers. Despite this vast accumulation of new information, much more must be learned before we can confidently describe the role of basophils, or of the closely related mast cells, in health or disease. It seems most unlikely that either cell exists for the purpose of destroying the organism in anaphylactic shock. Nonetheless, it is highly probably that basophil/mast cell function is closely related to the potent chemicals stored within their cytoplasmic granules. One likely possibility holds that small amounts of these chemicals are required for homeostasis (e.g., for regulation of the tone of the microvasculature) and that these cells function by releasing such substances continuously, as they are needed, in small aliquots rather than by explosive discharge. This hypothesis requires that basophils be capable of releasing their contents in piecemeal fashion. Such gradual release apparently occurs in delayed-type hypersensitivity reactions, but the mechanisms responsible for this form of degranulation have not yet been identified. This hypothesis also requires that physiological, rather than pharmacological, roles be found for histamine, heparin and possibly for other components of the basophils/mast cell granules. Progress in this direction has been extremely slow.